JPH04233992A - Ammonium pyrophosphate composition - Google Patents

Abstract

PURPOSE: To obtain the subject composition which can make a substrate flame- retardant in a manner advantageous in cost and time by dissolving solid phase II ammonium pyrophosphate in an aqueous solution of ammonium pyrophosphate and adding and reacting ammonia water to and with it.

CONSTITUTION: Liquid phosphoric acid is poured into a rotatable, water-coolable cylindrical container at a temperature of 60°C, phase II pyrophosphoric acid is added to it, and the container is started to be rotated and cooled to obtain a perfect crystal after 14 hr. Next, an ammonium pyrophosphate solution is sprayed over the solidified acid, the overflow is collected in another container, the collected liquid is mixed with water and ammonia to keep the pH at 7.0. The liquid portion is continuously sprayed and recirculated to continue the spray until all of the acid has been dissolved to obtain an ammonium pyrophosphate composition in which at least 70% of the phosphorus present therein exists in the form of pyrophosphate.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to phosphoric acid complexes, particularly ammonium pyrophosphate, and a method for producing the same, and further relates to a method for making a substrate flame retardant using a solution thereof.

0002

BACKGROUND OF THE INVENTION It is known to impregnate substrates such as textiles and wood with ammonium polyphosphate solutions for the purpose of imparting flame retardancy. This product is produced by the reaction of ammonia with polyphosphoric acid and contains, for example, 80-86% P2O5, especially 80.2
% or 82.0% P2O5 (see British Published Patent No. A-1504507). Other products have a degree of condensation of 3 to 30 and an atomic ratio of phosphorus to nitrogen of 1:0.5 to
Ammonium polyphosphate prepared from polyphosphoric acid 2 (UK Published Patent No. A-1069946)
(see issue). Such polyphosphoric acids include ortho, pyro, tripoly, tetrapoly and higher polyphosphoric acids, the proportions of which are determined solely by the total P2O5 content of the acid (Canadian Journal of Chemistry). of Chemi
34, p. 790 (1956)). In the acids described in GB-A-1504507, the amounts of ortho, pyro, tri and higher polyacids are approximately 15, 40, 25 and 20%, respectively.
However, the amounts of acid described in British Published Patent No. A-1069946 are approximately 0-15, 1-40, and 1-40, respectively.
In the range of 2-25 and 20-97%. It has been found that the ammonium polyphosphates of GB-A-1504507 are not entirely satisfactory when they are used to flame retardant resins bonded to wood-based panel products. Ta.

0003

SUMMARY OF THE INVENTION The present inventors have provided ammonium pyrophosphate with significantly reduced levels of phosphates other than pyrophosphate, a method for producing it by a simple process, and its use as a flame retardant. I found a way to use it.

[0004] Accordingly, in one aspect of the present invention, there is provided ammonium pyrophosphate in which at least 70% of the P2O5 content is present as pyrophosphate.

[0005] In a second aspect, the present invention provides a method for producing ammonium pyrophosphate, in which Phase II solid pyrophosphate has a pH of 6.
ammonium pyrophosphate at pH 6 to 10 to produce an aqueous liquid at pH 5 to 9 and subsequently reacted with ammonia to form ammonium pyrophosphate at pH 6 to 10, in which at least 70% of the P2O5 content is present as pyrophosphate. A phosphate solution can be obtained.

[0006] In a third aspect, the present invention further provides P
Provided is a method of flame retardant a flammable substrate comprising impregnating the flammable substrate with an aqueous solution comprising ammonium pyrophosphate, wherein at least 70% of the 2O5 content is present as pyrophosphate. . Preferably, the impregnated substrate is dried and then thermally cured.

The present invention further provides a combustible substrate and P
A flame retardant material is provided comprising ammonium pyrophosphate in which at least 70% of the 2O5 content is present as pyrophosphate.

Preferably, the ammonium polyphosphate contains as P2O5 at least 80% as pyrophosphate, less than 15% as tripoly and higher polyphosphates, and less than 8% as orthophosphate. , in particular at least 90% for pyrophosphates, less than 5%, preferably less than 3% for orthophosphates and others, and preferably less than 5% for tri- and higher polyphosphates.

Phase II solid pyrophosphate is described in the Kirk-Othmer Encyclopedia of Chemistry, 2nd edition, volume 15, page 241. This is preferably 79.7% in the presence of Phase II seed crystals.
of P2O5 (which has a composition corresponding to H4P2O7) (79
．． 7% liquid pyroic acid is approximately 46% pyrophosphoric acid, 20%
orthopyrophosphate, 20% tripolypyrophosphate and 14% higher polyphosphoric acid). Preferably, the crystallization solidifies all of the acid present. This is the choice when the liquid is at the preferred 79.7% P2O5 content, but can alternatively be recrystallized and pyrolysed from a mother liquor containing ortho, tri and higher polyacids. Acid crystals can be separated. Crystallization is usually
40-65°C, preferably 50-65°C, typically 6
Perform at 0°C.

In the crystallization process, the concentrated pyroic acid is preferably brought into contact with a cooled surface and solidified as a thick layer; alternatively (less preferably) the concentrated pyroic acid Crystals can be formed in a stirred body of cooled acid. The crystallization is advantageously carried out in a rotating crystallization drum so that the solid product forms on the cooled internal wall of the rotating drum.

The solid Phase II crystals, after being separated from the mother liquor (if present), are preferably contacted with an aqueous ammonium pyrophosphate solution. Preferably this is a recycled portion of the product. The solution has an initial pH of 6
~10, especially 8-10, the comparative ratio of crystalline to solution is such that when the liquid is no longer in contact with the crystals, the final pH
It is preferable that the number is 5 to 9, especially 6 to 8. This contact can be batchwise, in which all the crystals are in contact with all the solution, or semi-continuous, in which the solution is repeatedly passed over the crystals, but preferably, the pyroic acid is gradually leached out. A continuous method in which the solution passes over the crystalline material is preferred. This contact may be below 65°C, for example 20-40°C.

The liquid is then mixed with ammonia at a pH of 5-9 to produce a solution of ammonium pyrophosphate at a pH of 6-10. A portion of the solution is normally recycled, preferably after cooling, into contact with fresh crystallization, and the remainder may be removed as product.

Ammonium pyrophosphate solutions usually contain nitrogen atoms as ammonium ions and phosphorus atoms as phosphate in a ratio of 1 to 2:1. A particularly preferred ratio is 1.4 to 1.6:1.

In a preferred embodiment of the invention, the aqueous solution may contain a carbamic acid derivative having at least two amino groups per molecule. Such additives can improve the flame retardant leaching resistance of the finished product. Particularly useful as additives are urea, guanidine and dicyandiamide. Preference is given to using urea. The ratio of carbamic acid derivative to pyrophosphate may range from 3:1 to 1:1, most preferably from 1.5:1 to 2:1, on a weight basis.

Substrates that can be treated with the method of the present invention include wood, including wood panel products such as plywood and other particle boards such as wood sheet materials, chipboard, medium density fiberboard and strawboard. These particle boards include wood chips and resin bonded thereto. Of particular interest are particleboards with two or more layers of wood chips of different densities, especially sandwich structures with a lower density intermediate layer sandwiched between two higher density layers.

Impregnation of the substrate with the treatment solution can be accomplished by any conventional means convenient for the particular substrate type. Thus, the substrate of wood and wood products, such as particleboard, can be impregnated using soaking, dipping or spraying techniques, by brushing an aqueous solution onto its surface, or by pressure or vacuum impregnation methods.

The proportion of ammonium pyrophosphate mixture introduced into the substrate depends on the desired flame retardancy and flammability of the substrate. For wood and fibreboard,
It is desirable to incorporate 1 to 30% by weight of ammonium pyrophosphate, preferably 5 to 25% (the percentages are expressed based on the weight of dry ammonium pyrophosphate relative to the dry substrate).

The concentration of the aqueous ammonium pyrophosphate solution used in the impregnation step depends on the impregnation method compatible with the substrate and the amount of pyrophosphate desired to be added to the substrate. As a general rule, the concentration used can be from 0.5 to 20% by weight of ammonium pyrophosphate, for example from 10 to 15% (expressed as weight % of phosphorus pentoxide in the presence of water). The aqueous solution may contain additives conventionally applied to flame retardant or flame retardant wood products. Such additives include, for example, known wood preservatives such as disodium octaborate tetrahydrate and paraffin waxes, which are used to improve the dimensional stability of plank products.

After the impregnation step, the substrate can be dried and subsequently heat cured. The impregnated wood product can be dried, for example, by gradual heating to 30-80°C over a period of 12-120 hours. At the same time, the ambient humidity can be slowly reduced to obtain a treated product with a moisture content suitable for its end use. Optionally, thermal curing is performed at elevated temperatures (e.g. 80-110°C);
It can be carried out over a longer period of time (for example 4 to 8 hours).

Alternatively, the ammonium pyrophosphate solution can be mixed with the material for making the particleboard before or during the plank manufacturing process. This solution in this case accounts for 10-50% of the total weight of the boards forming the product, preferably 20-50% of the total weight of the boards forming the product.
It may contain 40%, more preferably 25-35% (as P2O5), and 5-15%, preferably 8-12%.

The planks can be produced by conventional pressure processes and by condensation of binding resins conventionally available in such processes, such as urea, melamine, phenol or resorcinol, with aldehydes (for example formaldehyde). or isocyanate resins.

Other substrates that can be treated by the method of the present invention include woven and nonwoven materials. These are typically cellulose-based substrates, such as cotton, linen, jute, hessian or regenerated cellulose materials,
For example, it is a rayon or viscose fabric or filament, but it can also be paper, cardboard or wallpaper. The substrate may also be based on cellulosic materials and other fibers that can be blended or mixed therewith, such as polyester or nylon, acrylics, acetate, polypropylene, silk or wool. The blend or mixture of these fibers may contain at least 50%, such as 70-100%, such as 50-80%, of cellulosic material.

[0023] The weight of the fabric is 50 to 1000 g/m2,
For example, it can be 80 to 500 g/m2. The fabric can be of pile or plain construction. This fabric may be plain or undyed;
Alternatively, it may be dyed and printed (especially in white or pastel colors). The fabric prior to impregnation is typically free of stains, sizes, natural waxes and applied finishes, but may include fluorescent brighteners.

[0024] Usually pH 5 to 8, for example 5.5 to 7.5.
The flame retardant material is then applied to the substrate by conventional procedures such as padding, soaking, spraying, and typically the wet pick-up level is between 50 and 150%, such as between 60 and 100%. Before drying and after squeezing out excess liquid, the total solids pickup is usually between 10 and 35%, such as between 25 and 30%.
% (based on the dry initial weight of the fabric). After impregnation, the substrate is subsequently dried. For example, the base of a textile is
2 to 40 minutes at 80 to 120°C, preferably 2 to 10 minutes. Drying can be by force application of dry air in any conventional dryer, such as a tenter. The amount of solids impregnated after drying is usually 8 to 25%, for example 10 to 20%.
% (based on the initial weight of the fabric).

The dried substrate is subsequently cured. This curing is performed at, for example, 120-170°C, e.g. 130-170°C.
C., for example 140 to 170.degree. C. or 147 to 170.degree. C., for 6 to 0.5 minutes, or 5 to 0.5 minutes. The combination of longer times and higher temperatures tends to cause discoloration and should be avoided.

Particularly when the ratio of carbamate derivative to pyrophosphate is high, a suitable temperature is 147 to
165°C, for example 147-160°C or 147-15
6 to 0.5 minutes, preferably 5 to 2 minutes at 5°C. In order to minimize the risk of any coloration, especially when the ratio of carbamic acid derivative to pyrophosphate is low, the dried substrate is preferably cured by heating at 120-147° C. for 6-0.5 minutes. It is. The combination of longer times and higher temperatures tends to cause discoloration and should be avoided. These suitable temperatures are 120-142°C, such as 124-142°C or 1
At a temperature of 28-138°C, 6-0.5 minutes, such as 6-1.5 minutes, but at a temperature of 138-147°C, 3.5-0.5 minutes.
minutes, e.g. 138-142°C or 142-14
At 7°C, 3.5 to 0.5 minutes can also be applied. 130-14
Curing at 0° C. for 4 to 2 minutes, for example 3.5 to 2.5 minutes, is preferred.

Curing at 147-170° C. with a high ratio of carbamic acid derivative to pyrophosphate
Although it has a higher curing efficiency than low temperature curing with a high proportion of pyrophosphate and a large amount of pyrophosphate in the impregnation bath, the latter is less prone to discoloration, especially on white or pastel fabrics.

Continuous curing is usually carried out by radiation, eg infrared heating, or injection of steam and/or hot air through or over the substrate, or by heating the substrate and a heated metal drum in a vertical stack. It can be carried out by contacting with, but preferably,
This curing may be by heating the substrate by impinging hot air onto the surfaces (preferably both surfaces, so that the heating is uniform). That is, preferably the substrate is
It may be continuously passed through a tenter with a thermostatically controlled oven in which heated air flows across the top and bottom surfaces of the substrate. The tenter provides the most uniform curing with the least amount of charring. In the case of a tenter oven, the curing temperature of the substrate is substantially the same as the temperature of the hot air stream. Typically, at the end of curing, the substrate is rapidly cooled by cooling air passing through or drawn through the substrate.

As a finished product, the cured fabric typically has a solids content of 6 to 25%, for example 8 to 20%, and usually 0.5 to 5% P, for example 0.5 to 4% P. , preferably 1-3% P, or 2-4% P. The finished fabric has reduced flammability compared to the untreated substrate and can pass the BS5852 test for ignition sources 0 and 1.

[0030] Conventionally used ammonium polyphosphates are produced via neutralization of polyphosphoric acid. The only effective method of making this in a preferred embodiment involves adding phosphorus pentoxide to water or further diluted purified phosphoric acid or diluted acid concentrate. Both of these methods are very expensive, both in terms of time and cost, and do not allow direct use of the easily cheaper wet process acid (P2O5 content of about 70%). In comparison, the manufacturing method of the present invention is carried out via a crystallization step used to purify the phosphate, allowing lower grade and less concentrated materials to be used more effectively, resulting in a direct An advantage arises. This material has an advantage over conventional ammonium polyphosphates in that it uses a suitable composition that does not require a precise P2O5 content of the acid to be initially prepared. Quality control is therefore substantially enhanced and simplified. As can be seen from the examples, ammonium pyrophosphate is at least as effective as ammonium polyphosphate on a weight/weight basis. Therefore, there is no extra phosphorus added to the substrate when it is processed.

[0031]

[Examples] The present invention will be explained below with reference to Examples. All parts and percentages are by weight unless otherwise specified. Example 1 250 parts of liquid phosphoric acid (79.6% P2O5) was
℃ in a cylindrical container that can be rotated and water cooled. 2
．． Added 5 parts of Phase II pyrophosphoric acid and began rotating and cooling. After 14 hours, complete crystallization occurred. Ammonium pyrophosphate solution (approximately 30% P2O
5, pH 7) onto the solidified acid,
The overflow was collected in a separate container. The spray rate was controlled to maintain the overflow at about 30° C. and a pH above 5.5. The collected liquid was reduced to about 30% P by adding water and ammonia.
Maintained at 2O5 and pH 7. The liquid part can be continuously circulated to the spray. Spraying continued until all acid was dissolved. This product has a p of 7.1
H (measured as a 2.5% solution) and 29.5% P
2O5 content and only 1.4 as orthophosphate
It contained %.

Example 2 Oven dried (overnight at 105° C.) wood corechip (1350 g) was placed in a drum mixer and mixed with diphenylmethane-4,4'-diisocyanate (81 g) in water (52 g). ) followed by ammonium pyrophosphate solution (150 g; 29.47% P2O5; N:P molar ratio 1.486; P2 present as orthophosphate
O5 was sprayed at 1.38%; pH 6.7; specific gravity 1.37) to form a mattress composition (moisture content 10
%). This was compressed at 180℃ and became 400mm x 400m.
A plank of m x 12 mm was formed. Total amount of water 135g instead of water and phosphate solution
These planks showed greatly increased flame retardancy (measured according to BS476 Part 7) compared to planks manufactured in the same way but using a mattress composition containing . This was substantially equivalent to that obtained in a comparative treatment using the same amount of ammonium polyphosphate. This treated plank has internal adhesion values of 770±40 (polyphosphate) and 740±40 (pyrophosphate) KPa and both 700±20k
It had a density of g/m3.

Example 3 Ammonium pyrophosphate solution (used in Example 2) 59% urea

27%
and water

A mixture containing 14% was prepared and used to treat the following fabrics. A. Cotton with plain fabric and batt print (240
g/m2 weight) B Plain weave, butt printed viscose (260 g/m2 weight) C 60:40 cotton/polyester weave (380 g/m2 weight)
2) After removing excess liquid, the wet pick-up weight is 26-28
%Met. Each fabric was subsequently dried at 110°C and 150°C.
Cure by baking for 3 minutes at . This sample contains an equivalent amount of ammonium polyphosphate,
There was no difference in color or texture when compared with similarly treated samples. All samples were tested with 0 ignition sources.
and passed the 1st BS5852 exam.

Claims (11)

[Claims] 1. An ammonium pyrophosphate composition consisting essentially of ammonium pyrophosphate, characterized in that at least 70% of the phosphorus present in the composition is present in the form of pyrophosphate. 2. At least 80% of the phosphorus is present in the form of pyrophosphate; less than 15% of the phosphorus is present in the form of tripolyphosphate or higher polyphosphates; and A composition according to claim 1, wherein less than % is present in the form of orthophosphate. 3. Solid Phase II pyrophosphate is dissolved in an aqueous solution of ammonium pyrophosphate;
For producing a composition according to claim 1 or 2, characterized in that the resulting aqueous liquid is reacted with ammonia to obtain an ammonium pyrophosphate solution having at least 70% of phosphorus present as pyrophosphate. Method. 4. The method according to claim 3, wherein the pH of the aqueous solution of ammonium pyrophosphate is in the range 5-9. 5. After the reaction of the aqueous liquid with ammonia,
The resulting ammonium pyrophosphate solution is 6 to 10
5. The method according to claim 3 or 4, having a pH in the range of . 6. Ammonium pyrophosphate solution contains nitrogen atoms (as NH4+ ions) and phosphorus atoms (as NH4+ ions).
6. A method according to any one of claims 3 to 5, containing PO43- as ions) in the range 1:1 to 2:1. 7. A method according to claim 3, wherein the aqueous liquid further comprises one or more carbamic acid derivatives having at least two amino groups per molecule. 8. The method of claim 7, wherein the ratio of carbamic acid derivative to ammonium pyrophosphate is in the range of 3:1 to 1:1 by weight. 9. Claim 7 or 8, wherein the carbamic acid derivative is urea, guanidine or dicyandiamide.
The method described in. 10. A flame-retardant material comprising a combustible substrate, characterized in that the substrate has been treated with a composition according to claim 1 or 2. 11. The material of claim 10, wherein the substrate comprises wood, wood material, textile, paper, cardboard or wallpaper.